The IRS GTO ULIRG Program

1
The IRS GTO ULIRG Program
2
The IRS GTO ULIRG program - details

• Of the 110 sources
• Flux limited 32 have S25 ? 0.3 Jy and log LFIR ?
  11.85 L?.
• We are observing all 32 in low and high-res
  modes.
• High redshift 27 have z ? 0.3.
• GTO1- 12/27 are being observed in low and
  high-res. GTO2 (all rest)
• High luminosity 11 sources have log LFIR ? 12.5
  L? .
• 10/11 are being observed in low and high-res..
• Mix of Far-IR colors 68 are cold (S25/S60 lt
  0.2) and 21 are warm.
• This is a higher fraction of warm sources than in
  a flux-limited survey (typically 10).
• GO Programs Veilleux et al., Lutz et al.,
  Imanishi et al., Verma et al. Sturtm et al.
• Additional IRS spectroscopy of 30 Template
  galaxies usual suspects
• Weedman et al. 2005, Brandl et al. 2006
  (submitted), Devost et al. 2006 (in prep)

3
AGN

• Diversity!
• in the mid-IR spectra
• of ULIRGs

Starburst
Embedded
4
ISO PHT-S spectra of BGS Sources
5
Arp220
6
Normalized BGS spectra
Armus et al. 2006
7

• Quantifying the contribution
• of accretion to a SMBH -
• and a Staburst
• to the total mid-IR flux
• AGN Tracer
• NeV at 14.3µm / 23.2µm
• (Ep97eV)
• Starburst Tracers
• NeII at 12.83µm
• (Ep21eV)
• Presence of PAHs
• 6.2µm EQW

Armus et al. 2006
8
Quantifying the contribution of the energy from
the AGN to the total IR luminosity
Armus et al. 2006
9
NeV not detected in deeply obscured ULIRGs Is
the AGN NLR fully obscured?
10
AGN thermal emission in mid-IR continuum

• Rising slope of thermal emission from the AGN
  torus from 2-5µm due to grains radiating in
  near-equilibrium
• Excess over starlight at 4-5µm
• Laurent Diagram

f(5µm)10Jy z0.004 D14Mpc
FSC153073252
Alonso-Herrero et al. 2003
f(5µm)7mJy z0.9 D5.8Gpc
11
Decomposition of the Infrared Spectrum

• Core of the method
• Assume absorption cross sections from Li Draine
  (2001) and an MRN grain-size distribution
• Calculate the opacities of PAH, graphitic and
  smoothed astronomical silicate grains.

• Each dust component has a quasi-fixed temperature
  i.e.. the fitting process is really an expansion
  into several temperature basis components.
• The number of dust components is fixed for the
  sample so that all galaxies are fit in a uniform
  manner.
• In addition to a 3500 K stellar blackbody and
  PAH component, we find that we need 3 additional
  continuum dust components with T400, 150, and
  30 K to accurately fit the entire sample.
• An AGN manifests its presence with the
  requirement of an additional hot dust component
  T800K (Laurent et al. 2000)
• Talk to Jason Marshall !

12
Decomposition of Arp220
TCold31K TWarm96K THot873K LHot/LTotal0.005 L
1-40/LTotal0.19 LPAH/LTotal0.004
13
Decomposition of Mrk231
TCold38K TWarm151K THot486K LHot/LTotal0.13 L
1-40/LTotal0.52 LPAH/LTotal0.006
14
Conclusions based on the BGS ULIRGs
AGN fraction estimates based on various methods
15
(No Transcript)
16
Quantifying the contribution of the energy from
the AGN Using the Laurent Diagram
Armus et al. 2006